1. Field of the Invention
The present invention relates to a communication terminal for coding a moving picture, and particularly to a communication terminal provided with a function of reducing loads of a discrete cosine transform and a quantization processing without degradation of picture quality.
2. Description of the Related Art
Coding of a moving picture is executed such that an inputted picture is separated into individual frames, and each frame is divided into macro blocks (MB) each including, for example, a rectangular region of 8 pixels×8 pixels. Various processings, such as discrete cosine transform (DCT), quantization, and Huffman coding, are performed on the MBs.
In coding a moving picture in this manner, the processing loads of the DCT and the quantization processing are very large. For this reason, various techniques to reduce the processing load have been considered.
For example, Jpn. Pat. Appln. KOKAI Publication No. 10-210480 discloses a technique in which when a picture signal is divided into blocks and coding is performed, an evaluation value of a predictive residual signal is obtained for each of the blocks, and it is judged that the block is an effective block when this evaluation value is equal to or greater than a threshold, while the block is judged to be an ineffective block when this evaluation value is less than the threshold, and predictive error information is not sent to the block judged to be ineffective.
By using this technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-210480, in a case where all coefficients obtained as a result of the quantization processing become zero, the DCT and the quantization processing can be omitted.
In recent years, a technique to code moving pictures called H.264 has been standardized. In this H.264 standard, since there are a plurality of coding modes, a situation arises in which the feature of a predictive error varies according to a selected coding mode. Thus, there is a concern that when a uniform method of reducing an amount of processing is applied to all coding modes, degradation of picture quality is caused.